1. Technical Field of the Invention
The present invention relates to a hot water supply system having a water heater and a ring pipeline, which extends through the water heater and in which heated water circulates under either the influence of gravity or driven by a pump.
2. Description of the Prior Art
State-of-the-art central water heating devices have a ring pipeline through which the water circulates and to which the taps are connected. Such a device is disclosed in German Patent Application No. DE 36 20 551. In such devices, assurance is provided that even after an extended break in the extraction of hot water from the tap, hot water is immediately available at the tap when required.
A ring pipeline is, however, very costly to install, particularly as it concerns the need to retrofit existing systems. If hot water is to be immediately available at all taps, the ring pipeline is to be provided directly along the taps, with the result necessarily being that its length is extended and, thus, the associated heat loss and a corresponding high pumping procedure is required to maintain the circulation. The ring pipelines can hereby be of differing cross-sections (e.g., large cross-section in the flow, compared with a smaller cross-section in return.)
If taps are connected to a hot water supply system via tap pipelines, the water contained therein cools with time if none is extracted. To avoid this problem, it is known to the art to continuously circulate the water by means of a circulation pipeline of substantially smaller cross-section than the tap pipeline. This is provided in the interior of the tap pipeline and ends open in the region of the tap, so that the radiation losses are reduced, resulting in a simple and low-priced, new installation or retrofitting of an existing system. Such an apparatus is disclosed in German Patent Application No. DE 37 10 771.
In such a system, however, it is necessary, for example, in the region of the circulating pump, that a part of the circulation pipeline extends outside of the tap pipeline, thus, this part necessarily consists of a pressure-proof material in order to resist the operating pressure of the water supply system. In the case of retrofitting an existing system, the circulation pipeline is introduced into the tap pipeline via a T-piece and advanced as far as the tap. With this procedure, however, there is the disadvantage that the advancing device is only controlled with difficulty and the circulation pipeline, opposite the introductory opening, initially impinges the inside of the tap pipeline at, more or less, a right angle, so that it constantly buckles and is often damaged when being advanced to the tap.
Additionally, it is problematic to equip long tap pipelines with such a circulation pipeline since, owing to the small cross-section with increasing pipeline length, a rapidly increasing feed pressure is required to sustain the circulation. Therefore, circulation pipelines are used in the interior of the tap pipeline, generally in combination with a local hot water generator which, when compared with a central water heater, is substantially less efficient as measured by effectiveness and operating costs.